As a method for bonding two members to each other, a bonding method using solder and a bonding method using an adhesive have widely been used. For example, solder is used for bonding an electronic component to a submount of a laser module and an adhesive is used for bonding an optical component to the submount of the laser module.
In a case where the electronic component and the optical component are bonded to the submount, the following problem occurs. That is, in a case where the electronic component is bonded to the submount by use of solder, it is necessary to plate a surface of the submount with gold in order to obtain sufficient bonding strength. However, a gold-plated surface of the submount makes it difficult to bond the optical component to the submount by use of an adhesive.
The following describes why it is difficult to bond a member to another member having a surface plated with gold. That is, bonding by an adhesive is typically strengthened by intermolecular force generated between molecules constituting the adhesive and atoms or molecules constituting a surface to be bonded of a member. However, since gold atoms are nonpolar atoms, in a case where the surface to be bonded is made of gold, it is impossible to strengthen the bonding by the adhesive by using the intermolecular force.
Patent Literature 1 discloses a bonding method as a technique usable for avoiding the problem. According to the bonding method disclosed in Patent Literature 1, an FIPG (Formed In Place Gasket) which has high bonding strength with respect to metal is used for bonding a metal member and a synthetic resin member to each other.